A pyrotechnic drive comprises a cylinder and a piston displaceably guided therein. A pinion can be provided, and the piston is provided with teeth which can engage into the pinion, in order to set it in rotation with a displacement of the piston.
The above-mentioned drive is used for example in a belt retractor where the main concern is to set a belt spool in rotation within the shortest space of time, in order to eliminate a belt slack. So as not to impair the other function of the unit which is to be driven, i.e. for example of the belt retractor, it is advantageous that the drive shaft can rotate freely, as long as the drive is not yet triggered. This is ensured in that the piston is not yet in engagement with the pinion by its teeth in the initial state. However, it must be ensured that with the run-in of the teeth into the pinion, the first tooth of the piston teeth hits into a tooth gap of the pinion.
German Patent Application DE 198 46 227 shows a generic drive in which to solve the said problem the first tooth of the piston teeth is constructed as a half-tooth with a shortened tooth head.
The invention provides a further pyrotechnic drive, in which a reliable run-in of the piston teeth into the pinion is ensured.